1. Field of the Invention
The present invention relates to monomers derived from perhalogenated sultones, to the process for their preparation, to the polymers obtained from said monomers and to their use for the production of ion-conductive materials.
2. Discussion of the Background
Compounds ROCF.sub.2 CF(CF.sub.3)SO.sub.2 F are known, in which R is an optionally halogenated alkyl group containing a vinyl double bond, an acetylenic bond, an epoxy group or (CH.sub.3 --CH.sub.2 --O).sub.2 P(O)--CH.sub.2 --CH.sub.2 -- or CH.sub.3 --CH.sub.2 --O--P--F(O)--CH.sub.2 --CH.sub.2 groups, as is a process for their preparation from a cyclic fluorinated sultone (Chen et al., J. of Fluorine Chemistry, 48 (1990) 107-122); Chen et al., J. of Fluorine Chemistry, vol. 46, 1990, p. 21-38; Chen et al., J. of Fluorine Chemistry, vol. 46, 1990, p. 39-56). Compounds in which a --SO.sub.3 M group, M being H, Li, Na, NH.sub.4 or K, is attached to a radical R.sup.1 R.sup.2 --N--C(O)--CH--(CH.sub.2).sub.n --COOM, n being 0 or 1, R.sup.1 and R.sup.2 being alkyl groups, are described in U.S. Pat. No. 4,490,308 (D. W. Fong et al.). EP-A-0124378 (Du Pont De Nemours) describes monomers CH.sub.2 .dbd.CH--CF.sub.2 --CF.sub.2 --OCF.sub.2 --CF.sub.2 --SO.sub.2 F, copolymers of these monomers with ethylene and the use of these copolymers as electrically insulating materials. Compounds resulting from the reaction of a difluoroiodomethanesulfonyl fluoride with an olefin in the presence of copper, for example n--Bu--CH.dbd.CH--CF.sub.2 --SO.sub.2 F, Me--C(CH.sub.2)--C(CH.sub.3).sub.2 --CF.sub.2 SO.sub.2 F or CH.sub.2 .dbd.CH--(CH.sub.2).sub.2 --CH.dbd.CH--CF.sub.2 SO.sub.2 F, are described in Chem. Abs., vol. 114, 1991, No. 23718b, Huaxue.
European Patent No. 13199 (Armand and Duclot) discloses polymeric electrolytes obtained by dissolving a salt M.sup.+ X.sup.- in a solvating polymer containing heteroatoms, M.sup.+ denoting H.sup.+, a metal cation, an organic cation of the ammonium, amidinium or guanidinium type, X denoting an anion with a delocalized electronic charge, for example Br.sup.-, ClO.sub.4.sup.-, R.sub.F SO.sub.3.sup.- or (R.sub.F SO.sub.2).sub.2 N.sup.-, R.sub.F denoting a perfluoroalkyl or perfluoroaryl group. These polymeric electrolytes have many applications, in particular in the field of electrochemical generators, light-modulating systems (M. Armand et al., EP-87401555), sensors, for example for selective or reference membranes (A. Hammou et al., FR-86.09602). Many investigations have been carried out, in particular to improve the conduction properties of these materials. They have resulted, for example, in the formation of copolymers based on ethylene oxide (M. Armand et al., FR-83.09886) or of networks crosslinked by urethane bridges (H. Ch eradame et al., FR-8007135, U.S. Pat. No. 4,357,401). However, these materials have a common characteristic of exhibiting a mobility of the X.sup.- anion which is, in most cases, greater than that of the M.sup.+ cation. This property is a disadvantage, in particular in the case of electrochemical systems in which the electrode reaction involves the M.sup.+ cation. The current flow gives rise to the formation of a dissolved salt concentration gradient which increases the resistivity of the electrolyte and can bring about the formation, near the interfaces, of polymer-salt stoichiometric compounds exhibiting an insufficient ionic conductivity.
A number of attempts have been made to synthesize polymers containing anionic groups attached to the macromolecular chain. The ionophores containing alkylsulfonate RSO.sub.3.sup.- groups, carboxylate groups or perfluorocarboxylate --R.sub.F CO.sub.2.sup.- groups [D. J. Bannister et al., Polymer 25, 1291 (1984); E. Tsushida et al., Macromolecules 21, 96 (1988)] are, however, very slightly dissociated in solvating polymers of the polyether type such as polyethylene oxide. The ionic conductivities obtained with such materials are thus very low and do not allow any practical applications to be envisaged.
Furthermore, perfluorosulfonic --R.sub.F SO.sub.3.sup.- groups constitute the ionophore groups of the ion exchange membranes of Nafion.RTM. type. Such membranes, as well as the monomers from which they are obtained, are described, for example, in DE-A-3047439 (Asahi Kasei Kogyo KK), DE-A-2461675 (Du Pont De Nemours), U.S. Pat. No. 3,718,627 (W. G. Grot) or in U.S. Pat. No. 3,714,245 (R. Beckerbauer). The crosslinkable part of the monomers and the backbone of the polymers forming the membranes are perfluorinated. These polymers exhibit ionic conductivity only in the presence of polar solvents such as water, alcohols and propylene carbonate; the perfluorinated network of this type of polymer does not actually have any solvating or dissociating character, in contrast to the polyethers.
Polymers --(CX.sub.2 CXR).sub.n -- or --(CXRCXR).sub.n -- in which X is H or F and R denotes --(CX.sub.2).sub.m --SO.sub.3 H, and their use as electrolyte in fuel cells are described in Chem. Abstr., vol. 117, 1992, No. 27945h Matsushita.
WO-A-9202571 (SRI International) describes ion-conductive polymers bearing grafted anions --X--Y.sup.- M.sup.+, it being possible for X to be CF.sub.2 or CFR.sub.F, it being possible for Y to be SO.sub.3 and M.sup.+ being a cation. The backbone of the polymers is derived from a linear polymer which has mobile hydrogens. It may be, for example, a backbone of the polyether, polyester, poly(ethylene)imine, polyphosphazene or siloxane type. The polymers may be obtained either by grafting appropriate groups onto any polymer chain which has mobile hydrogens, or by polymerizing monomers containing an oxazoline ring bearing a --SO.sub.2 F group.